Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. These air pollutants may include oxides of nitrogen (NOx). Due to increased attention on the environment, exhaust emission standards have become more stringent. The amount of NOx emitted from an engine may be regulated depending on the type of the engine, the size of the engine, and/or the class of the engine.
One method implemented by engine manufacturers to comply with emissions regulations has been to reduce NOx levels in engine exhaust using a process called selective catalytic reduction (SCR). In SCR, a gaseous or aqueous reducing agent may be added to the exhaust gas of an engine. The mixture may be absorbed onto a catalyst. The reducing agent may react with NOx in the exhaust gas to form water and nitrogen gas.
In order to help promote mixing between the reducing agent and the exhaust gas, the reducing agent may be introduced into the exhaust gas by a reducing agent injector. The reducing agent injector may include a nozzle that extends into the flow path of the exhaust gas. The reducing agent may be sprayed into the exhaust gas using the nozzle, allowing the reducing agent and the exhaust gas to mix, which may help to encourage the reduction reaction. However, over time, debris may form on or in the nozzle, causing the nozzle to clog. If the nozzle becomes clogged, it may be difficult or impossible to introduce the reducing agent into the exhaust gas, and may eventually prevent SCR from taking place.
One method for purging an injector is described in U.S. Pat. No. 6,913,005 to Linna et al. (“Linna”). Linna discloses an injector including a capillary flow passage, and a heat source arranged along the capillary flow passage to heat a liquid therein. The heat applied is sufficient to convert a portion of the liquid from the liquid state to a vapor state. The portion of liquid fuel to be converted to the vapor state is controlled to achieve minimal exhaust emissions. The vaporized fuel can be supplied to a combustion chamber of an internal combustion engine during cold-start and warm-up of the engine and reduced emissions may be achieved. However, the injector in Linna is used for fuel injection, rather than for reducing agent injection. Further, the heat source in Linna is adapted for vaporizing liquid fuel, and is not disclosed as being capable of burning off solid residue that may be clogging the injector.
The system and method of the present disclosure solves one or more of the problems set forth above.